if you out of the 14 days quarantaene.... You can travel where ever you want... Later is the question if its a red Zone you need to show an other test.. Just go and check if chiang Mai is a RED zone....
Don't need an agent.. Take the convid 60 days first and then look if you can get an ED visa. With a school who has connections to tge immigration. Cost around 30 k per year... Need to go to school learning.. Easy